Multi-rate Dsp before Discrete-time Signals and Systems

If discrete-time (d.t.) signals and sequences are viewed as distinct, with d.t. signals simply trains of impulses in continuous time (c.t.) whose areas, systematically normalized, are the sample sequences realizing those signals in computational DSP, then basic c.t. signals and systems is easily followed by an introduction to multi-rate systems for processing d.t. signals. Classic d.t. signals and systems then becomes follow-on material about realizing such systems computationally.